It is often necessary to apply a frictional coating to the surface of a machine's feeding or dispensing mechanisms that contact the material fed into or discharged from the machine. The frictional surface must have a coefficient of friction high enough to enable each mechanism to properly grip and guide the material but not so high as to damage the material. The coated surface wears away over a period of use to the point where its reduced coefficient of friction no longer permits proper feeding or dispensing. If the material is abrasive, as paper is, the wear is increased. It then becomes necessary to rejuvenate the frictional surface to its original characteristics.
It is well known in the art that through the use of a flame spray process a frictional surface can be created on a new part or a worn frictional surface can be rejuvenated on an old part. Flame spraying is a metalizing process whereby a frictional surface is created by spraying droplets of the desired surface material onto a machine part's surface. This process can be repeatedly used on the same part to restore the frictional surface which wears away during its service life, but small differences in the finished surface make major differences in its operating characteristics, and no measuring system is known. The coatings may be pure metal or ceramics such as oxides, carbides or other hard surfaces, or alloys.
For example, rolls used in the paper industry on machines for rolling paper into the width and diameter desired by the customer are often coated with an abrasive material so that they can grip and maintain the correct amount of tension during the paper rolling process, without slipping or tearing. The coating prevents slippage of the paper web on the bed roll of the winder during the construction of the finished roll. A properly rolled paper roll is tightly wound so it will not telescope during shipment. However, paper is an abrasive material. Thus the frictional surface on the roll typically wears out after a period of use. So that the roll can be reused, a new frictional surface is applied by a flame spray process.
Our traction analyzer measures the frictional surface of the coated machine part after the droplets of surface material have been applied through the flame spray process. Through its use the required coefficient of friction and service life attained by applying a given coating under known conditions can be estimated, and preferred conditions for treatment of each feeding or dispensing mechanism can be determined. It is an objective of our invention to enable the measurement of a machine part's surface in order to establish uniformity in the flame spraying process and in defining recoating intervals for particular workpieces and customers. Another objective of our invention is to provide such a measuring device that produces consistent and accurate data representing the frictional qualities of the surface's coating. Such data may be used to determine when re-surfacing is needed, or to characterize the results of re-surfacing to verify that a prescribed frictional characteristic has been attained. On a surface with a known characteristic, unknown papers may be tested to qualify them as test paper strips. It is a further objective of the invention to provide such a measuring device that is portable, compact, and easy to use.